Portable data collection devices are widely used in manufacturing, service and package delivery industries to perform a variety of on-site data collection activities. Such portable data collection devices often include integrated bar code dataform readers adapted to read bar code dataforms affixed to products, product packaging and/or containers in warehouses, retail stores, shipping terminals, for inventory control, tracking, production control and expediting, quality assurance and other purposes.
Bar code dataforms come in a variety of different formats including one and two dimensional bar codes, matrix codes and graphic codes, as well as words and numbers and other symbols, which may be printed or etched on paper, plastic cards and metallic and other items. For example, a one dimensional bar code dataform typically consists of a series of parallel light and dark rectangular areas of varying widths. The light areas are often referred to as "spaces" and the dark areas as "bars". Different widths of bars and spaces define different characters in a particular bar code dataform.
Data originally encoded in a dataform is recovered for further use in a variety of ways. For example, a printed bar code may be illuminated to derive reflectance values which are digitized, stored in buffer memory and subsequently decoded to recover the data encoded in the bar code. The printed bar code may be illuminated using a laser, an array of LEDs, ambient light, or the like. The light reflected from the printed bar code typically is captured using a photosensor such as, for example, a CCD detector or CMOS detector.
A problem associated with conventional dataform readers is that the readers are designed to read dataforms located within a limited range therefrom. For example, a dataform reader may be designed to read dataforms located within the range of three inches to twelve inches from the reader. The maximum distance at which a dataform reader is able to read a dataform is limited by a resolution of the photodetector used to capture the dataform. For example, using a conventional 640 horizontal pixel photosensor, one dimensional bar code dataforms can be read so long as the distance the reader is placed from the dataform is such that the 640 horizontal pixels are suitable to distinguish among the narrowest bars and spaces forming the dataform. As the dataform reader is moved further away from a dataform, the images of the bars and spaces appear smaller at the photosensor thereby limiting the range at which the dataform reader is able to read a dataform.
One way to allow the dataform reader to read the dataform at longer distances is to increase the resolution of the photosensor. For example, rather than providing 640 horizontal pixels, the photosensor may include 1000 or more horizontal pixels. In this manner, the photosensor is able to distinguish among smaller features of the dataform thereby enabling reading of dataforms located farther away. A significant drawback to increasing the number of horizontal pixels on the photosensor is that a width of the photosensor becomes proportionately larger in order to accommodate the additional pixels. As the width of the photosensor increases, so does the overall width of the reader module. Unfortunately, due to customer demand for smaller and more compact dataform readers, the ability to increase the width of the reader module is often not a feasible option.
Accordingly, there is a strong need in the art for a dataform reader which is capable of reading dataforms at longer distances which overcomes the aforementioned drawbacks.